For the long-lasting impact of CoRoT's planet findings, precise knowledge of the times of their transits is of vital importance for any future observing campaigns. Currently, there are several CoRoT-planets with timing errors that are already critically large, which would impede their observations within a few years. This led to the proposal of a systematic ground-based revisit of the transits of nearly all CoRoT planets to refine their ephemeris, using several telescopes located in the Canary Islands and elsewhere. As secondary objectives, more precise planet characterizations, from period or transit shape variations and from use of a well-defined passband may be obtained. The first observations for this program have recently been taken, and their impact on the precision of the ephemeris of the CoRoT planets is shown.